1. Field of the Invention
The present invention relates to a machine tool for advancing and retreating a machining unit from a work supported on a work support table to perform machining of a work, and more particular, to a cover construction.
2. Description of the Related Art
Generally, a machine tool comprises a work support table for supporting a work being machined, and a machining unit capable of mounting and dismounting of tools, which perform machining, such as drilling or the like, of the work. The machining unit is composed of a Z-axis saddle mounted on a bet to be able to reciprocate in a Z-axis direction (longitudinally), a column mounted on the Z-axis saddle, and a machining head mounted on the column to grasp tools. And the machining unit is advanced to perform machining of a work, and when machining is terminated, the machining unit is retreated. Also, the column is mounted on the Z-axis saddle to be able to reciprocate in a X-axis direction (laterally). Further, there are some configurations, in which a X-axis saddle for reciprocation relative to the column in a Y-axis direction (vertically) is mounted, the machining head is mounted on the Y-axis saddle, and the machining unit is moved in three axial directions, that is, X-axis direction, Y-axis direction, and Z-axis direction.
While the machining head performs machining of a work, coolant containing a cutting oil for cooling and lubrication of tools and a work is supplied. When such coolant and chip enter into a machine region on a side of the machining unit from the machining head, a harmful influence is exerted on various sensors and limit switches provided on the machining unit, or slide members, seal members, or the like on X-axis, Y-axis, and Z-axis drive mechanisms. Therefore, a cover device is provided between the machining unit and a work support table. There has been heretofore proposed as such cover device an arrangement, in which an opening window for taking the machining head in and out in a X-axis direction (longitudinally) is provided on a stationary-side cover for compartment and formation of a machining room of a work, and a movable cover for shielding to prevent scattering of coolant outside from the opening window during machining of a work is provided on an outer peripheral surface of the machining head to be close to an opening window of a compartment cover. A configuration (JP-UM-A-4-115554) similar to the conventional configuration is shown in FIG. 3.
Also, a conventional cover device for machine tools is disclosed and proposed in JP-A-6-210531. The cover device is constructed such that a cylindrical-shaped opening of a protective cover surrounding a periphery of a machining head is fitted onto an opening window of a compartment cover in a manner to be able to advance and retreat.
Since the conventional cover device, disclosed in JP-UM-A-4-115554, for machine tools is not constructed such that a movable cover is brought into close contact with the opening window of the compartment cover during machining of a work, however, there are caused problems that sealing is made incomplete, and a part of coolant enters into a machine region on a side of the machining unit because the movable cover is opened downward. Further, the cover device cannot cope with the case where a machining unit is of a type, in which tools are driven left and right, and up and down. In recent years, coolant as developed has an adverse influence on equipments such as sensors, limit switches, and so on, and seal members, and so a solution therefor has been demanded.
Meanwhile, the cover device, disclosed in JP-A-6-210531, for machine tools is not constructed such that the cylindrical-shaped opening of the protective cover is brought into close contact with the opening window of the compartment cover during machining of a work. Therefore, the machining unit is retreated into a machine region in a state, in which coolant and chip adhere to an outer peripheral surface of the cylindrical-shaped opening, so that the machine region is made dirty. Besides, since an inside of the cylindrical-shaped opening is put in an opened state, coolant, chip, and scraps accumulate therein to be taken into the machine region during retreating of the machining unit while coolant and chip remain adhered to a peripheral surface of the machining head.